1. Field of the Invention
The present invention relates to a light emitting display and a scan driver, and more particularly, to a light emitting display and a scan driver for outputting a scan signal and an emission control signal, in which the scan driver provided in the light emitting display includes a first buffer for outputting the emission control signal, the first buffer being smaller than a second buffer for outputting the scan signal, thereby decreasing the size of the scan driver.
2. Discussion of Related Art
A thin and lightweight flat panel display has been widely used for monitors of various information terminals such as personal computers, mobile phones, personal digital assistants, etc. A flat panel display can be classified into a passive matrix type flat panel display and an active matrix type flat panel display according to methods of driving a pixel of the display. In the flat panel display, a displaying area includes a plurality of pixels arranged in a matrix format on a substrate. Each of the pixels is connected with, and selectively receives data signal from, a scan line and a data line to display an image. When resolution, contrast, operation time, and so on are taken into consideration, the active matrix type flat panel display capable of selectively switching the pixels by a unit pixel has been mostly used.
A flat panel display can also be a liquid crystal display (LCD) using a liquid crystal panel, an organic light emitting display using an organic light emitting device (OLED), a plasma display panel (PDP) using a plasma panel, etc.
Particularly, the OLED can emit light by itself on the basis of recombination of an electron and a hole and has a fast response time that is more similar to a cathode ray tube (CRT) than to a light emitting display requiring a separate light source, such as the LCD. Thus, the OLED has become very important.
FIG. 1 is a plan view of a configuration of a conventional light emitting display.
Referring to FIG. 1, the conventional light emitting display includes a pixel area 10 having N×M pixels 11 and for displaying an image corresponding to light emissions of the pixels 11; a scan driver 20 for supplying scan signals and emission control signals to the pixel area 10; and a data driver 30 for supplying data signals to the pixel area 10.
The pixel area 10 includes a plurality of scan lines S1, S2, S3, . . . , SN−1, SN (where ‘N’ is a natural number); a plurality of data lines D1, D2, D3, . . . , DM−1, DM (where ‘M’ is a natural number) arranged perpendicularly to the plurality of scan lines S1, S2, S3, . . . , SN−1, SN; and the N×M pixels 11 formed adjacent to regions where the plurality of scan lines S1, S2, S3, . . . , SN−1, SN and the plurality of data lines D1, D2, D3, . . . , DM−1, DM are crossed with each other.
Further, the pixel area 10 receives the scan signals through the plurality of scan lines S1, S2, S3, . . . , SN−1, SN, and allows the pixels 11 disposed on a predetermined row corresponding to a received scan signal to receive the data signals.
The scan driver 20 supplies the scan signals and the emission control signals to the pixel area 10 in sequence through the plurality of scan lines S1, S2, S3, . . . , SN−1, SN and a plurality of emission control lines (not shown), so that all rows of the pixel area 10 are sequentially selected corresponding to one frame and sequentially controlled by the emission control signals.
The data driver 30 is connected to the plurality of data lines D1, D2, D3, . . . , DM−1, DM, and supplies the data signals to the pixel area 10 through the plurality of data lines D1, D2, D3, . . . , DM−1, DM, so that a data signal is supplied to each pixel 11 selected by a scan signal, thereby displaying an image corresponding to the data signal on the pixel area 10.
FIG. 2 is a block diagram of a scan driver provided in a conventional light emitting display. Referring to FIG. 2, the scan driver 20 includes a shift register 21 for outputting a plurality of signals in response to an input signal; an operator 22 for creating scan signals and emission control signals based on the signals outputted by the shift register 21; and a buffer unit 23 for receiving the signals outputted by the operator 22 and for outputting them as buffered signals.
The operator 22 receives the plurality of signals from the shift register 21 and performs an operation to output the plurality of scan signals s1, s2, s3, . . . , sn−1, sn (where ‘n’ is a natural number), and the plurality of emission control signals (not shown). Each of the scan signals s1, s2, s3, . . . , sn−1, sn is transmitted to a switching transistor (not shown) of a pixel, thereby allowing a data signal to be transmitted to the pixel. Each of the emission control signals is transmitted to a gate electrode of an emission control transistor (not shown), thereby allowing a driving transistor (not shown) to switch a driving current that corresponds to the data signal. The driving current is supplied to an OLED.
The buffer unit 23 increases the intensity of the scan signals s1, s2, s3, . . . , sn−1, sn and the emission control signals created by the operator 22, and outputs them to the pixel area 10. When the scan signals are directly transmitted from the operator 22 to the pixel area 10 without passing through the buffer unit 23, the scan signals, which are relatively distant from the operator 22, are not smoothly transmitted to the pixels 11. Therefore, the intensity of each of the scan signals and the emission control signals is increased by the buffer unit 23 connected to the operator 22, and then transmitted to the pixel area 10.
In the above described light emitting display, the size of the scan driver 20 and the interval of the scan lines are determined according to the sizes of the buffer unit 23. That is, in a case where the size of the buffer unit 23 becomes large, the size of the scan driver 20 is enlarged, and the intervals of the scan lines are widened. Because of this, as the size of the scan driver 20 is increased, power consumption is increased. Accordingly, as the intervals of the scan lines are widened, each of the pixels 11 is enlarged.
Particularly, when the light emitting display is a large-sized screen, the size of the buffer unit 23 is increased, so that the intervals of the scan lines are widened, thereby enlarging the size of each of the pixels 11. In this case, it is difficult to get a high definition. Further, the power consumed in the buffer unit 23 is increased, so that the light emitting display consumes relatively more power in displaying an image.